A Pulsed Electron Source for the HITRAP Cooler Trap

The HITRAP Cooler Trap will store highly charged ions and cool them to a temperature of 4 K for delivery to precision experiments [1]. The trap is preceded by a decelerator complex able to slow ion bunches delivered by the ESR from a specific kinetic energy of 4 MeV/u down to 6 keV/u [2]. The Cooler Trap is designed as a 23-ring cylindrical Penning trap, providing the ability to simultaneously store positively charged ions and electrons. Application of electron cooling will decrease the thermal energy of the trapped ion bunch to 10 eV. Subsequently, electrons will be expelled from the trap in order to avoid excessive ion loss by recombination reactions [3]. The final ion temperature of 4 K will be reached by resistive cooling at the trap ring electrodes [2]. A pulsed electron source providing more than 2 · 10 particles per bunch has been developed at the Max-Planck-Institute for Nuclear Physics (MPIK) and will allow efficient electron filling of the Cooler Trap.